Ginkgo leaf extract is derived from the leaves of the ginkgo biloba tree, which is native to the Tianmu Shan mountain reserve in eastern China. The large ginkgo biloba tree, also known as the Maidenhair tree, generally reaches a height of 80 feet (about 24 m) and features fan-shaped leaves and irregular branching. Ginkgo leaf extract is typically used as an herbal medicine to treat circulatory problems and symptoms associated with Alzheimer's disease, including memory loss. The effectiveness of ginkgo leaf extract to treat these conditions has not been conclusively established, but the chemicals comprising ginkgo leaf extract generally have beneficial properties.
Generally, ginkgo leaf extract contains flavonoids — a plant pigment that gives the ginkgo biloba leaf its color. When consumed, flavonoids typically serve as antioxidants in the body, thereby protecting the heart muscle, nerves, blood vessels, and retina from the harmful effects of free radicals. Flavonoids also enhance the antioxidant properties of vitamin C and interrupt the function of some viruses and bacteria.
Another chemical in ginkgo leaf extract is terpenoid — a fragrant compound that improves blood flow by dilating blood vessels and reducing platelet clumping. Terpenoids also help proteins bind to cell membranes by attaching a hydrophobic section onto the protein. Several molecules that are required for biological processes are typically derived from terpenoids, including steroids and sterols.
The ginkgo leaf extract typically is available as a capsule, tablet, or liquid extract. Standardized extracts usually contain 24 to 32 percent flavonoids and six to 12 percent terpenoids. A tea prepared from the dried leaves of the ginkgo biloba tree is not as potent as the standardized extract, but it can be effective at alleviating some ailments.
A recommended dosage to improve memory and cardiovascular function is typically 120 milligrams of standardized ginkgo leaf extract daily. If the conditions are severe, up to 240 milligrams daily, divided in three doses is generally recommended. It may take up to six weeks for a person to notice any improvement in function.
Possible side effects of ginkgo extract include headaches, skin irritation, and dizziness. People with epilepsy may experience seizures if they take ginkgo extract, and pregnant women should avoid ginkgo extract because of the possible risks to the baby. Ginkgo extract may interact with blood-thinning drugs to prolong healing time and bleeding. For this reason, it is generally recommended that a person stop taking ginkgo extract two days prior to any scheduled surgery. Ginkgo extract can also interact with antidepressants, which could lead to a dangerous condition known as serotonin syndrome.